One of the fundamental problems in the realization of an organic light-emitting diode (OLED) flat panel screen is the transport of charge carriers from the backside electrode into the organic layer being hampered by the Schottky barrier at the interface. Field emission display devices, based on Fowler-Nordheim electron emission from point sources such as carbon nanotubes, face the problem of homogeneous emission currents. Both device types, as well as the currently available thin film technology (TFT) liquid crystal displays, suffer from the need of a large number of transistors used to address their pixels, namely at least one transistor per pixel for black-white displays.
Another fundamental problem in the realization of polymer LED based flat panel screens is the addressed injection of charge carriers.
U.S. Pat. No. 4,601,971 of B. Lischke proposed to make use of the basic principle of tunnel cathodes as electron sources for e-beam lithography masks. These known e-beam masks are produced by structuring a master wafer with e-beam lithography such that the master provides a static pattern of electrons which can be projected onto many target wafers reducing costs in e-beam lithography. Such an e-beam mask was realized recently in semiconductor-insulator-metal (SIM) technology, see R. Tromp et al. Appl. Phys. Lett. 73, 2835 (1998). The principle relies on tunnel cold-cathodes, where electrons tunnel through an oxide layer separating two electrodes. The positive electrode is thin compared to the mean free path of electrons in the electrode material such that the tunnel electrons travel ballistically through this electrode. If the kinetic energy, given by the applied tunnel voltage, is larger than the work function of the electrode material ballistic electrons are emitted into vacuum. These known e-beam lithography masks however suffer from the limitation that they are “static”.